Raising animals has become a big business. In North Carolina alone, for example, the poultry, swine and dairy businesses are worth about $4 billion annually, and employ at least about 40,000 people directly. This translates into about 4,000 farms in North Carolina alone having facilities devoted to swine, each of which must conform to the appropriate environmental regulations. The present technological standard is a system utilizing an anaerobic lagoon, and most facilities are so equipped. While these systems do act to contain much of the waste, they leave something to be desired.
For swine, a typical lagoon system would be described as follows: the farm has several barns which have floors made of slats and a collection basin under each building. The animals are housed in the barns, and their feces, slops, urine and spilled drinking water fall through the slats into the collection basin. Each barn also has two 400 to 800 gallon flush tanks. Every three to six hours, about 800 to 1,600 gallons of water per barn are dumped into the collection basin, which washes the waste by gravity feed to an anerobic lagoon. Such a system is described in U.S. Pat. No. 4,913,095, "Flushing System for Hog Houses", issued to Morrow, et al. Apr. 3, 1990. The flush tanks are then refilled using water from the top of the lagoon. In an alternative system, referred to as a pit-recharge system, about two feet of water is kept under the barn in an enlarged version of the collection basin. This pit has an outlet which is opened on a weekly basis to allow the water to drain to an anaerobic lagoon. The pit is then refilled using water from the lagoon.
In theory, the solids in a lagoon settle out and are anaerobically digested over time by benign bacteria. After a certain amount of time, the top layer of water is purified enough to allow it to be drawn off and reused, either as wash water, or as water for crops. In practice, the quality of the water drawn off is not good enough to make it useable for all crops, and when the water is sprinkled on a field, it releases noxious odors. Further, the quality of water is not good enough to be used as drinking water for the animals, so there is a steady addition of water to the system due to the spillage from the fresh water system as well as water in the form of urine and feces from the animals. The rate of evaporation and draw-off of water are often less than the rate of influx of water as well as solids into the lagoon. As a result, the lagoon gradually fills up.
A typical lagoon might be twelve feet deep and contain about 10 feet of water, and 1200 tons of solids. Such a lagoon also contains a large amount of ammonia, nitrates, nitrites and phosphorus, and may on occasion contain disease-causing bacteria. If rainfall is unusually heavy, or if the liner for the lagoon cracks, significant amounts of pollutants can be released, possibly rendering water wells on neighboring land unfit for use, causing an overgrowth of algae in runoff streams, or even resulting in fish kills in rivers. Lagoons release noxious odors into the air, and have been associated with acid rain.
As a result of the difficulties of managing lagoon systems, several states have already issued moratoriums on the building of new lagoons, and have mandated the development of new technologies, and some progress has been seen. A variety of technologies have been proposed.
One class of technologies involves the use of microorganisms to digest the waste, in imitation and extension of natural processes. Such systems are well known, and they as well as various improvements thereon are described in any number of references, including U.S. Pat. No. 5,013,441, "Biological Nutrient Removal with Sludge Bulking Control in a Batch Activated Sludge System, issued to Goronszy May 7, 1991, which relies on digestion steps accomplished by both aerobic and anaerobic bacteria. U.S. Pat. No. 5,755,852, "Bioconverted Nutriet Rich Humus", issued to Northrop May 26, 1998 relates to a process wherein solids in an aqueous slurry of animal excrement are settled or precipitated in a solids ecoreactor and treated in a bioreactor both by aerobic and anaerobic processes to bioconvert soluble phosphorus, nitrogen and organics. U.S. Pat. No. 5,637,219, Means for Continuous Digestion of Organic Matter issued to Robinson, et al. Jun. 10, 1997 relates to a multistage process for biological and chemical digestion of waste, which utilizes a reaction vessel having separate control of the reaction conditions for different processes in different chambers. U.S. Pat. No. 5,395,529 "Apparatus for the Treatment of Sewage issued to Butler Mar. 7, 1995 relates to an improved rotating biological contactor for removing particulates or solids from sewage effluent instead of a settling tank in a bacteria-dependent process. The improved systems tend to be elaborate, requiring costly installation and supervision.
Other processes which do not rely on bacterial action have been explored. For example, U.S. Pat. No. 4,214,887 "Sewage and Waste Water Treatment" issued to van Gelder Jul. 29, 1980 relates to the use of a hydrocyclone and 20 micron filter along with a 5 micron filter in combination with an ozonator. This process is designed for streams with a relatively low solids load of about 300 ppm, and, without more, would be impractical in the present situation, where total solids loads of 1500 ppm may be encountered.
Processes which are primarily chemical have been explored. For Example, U.S. Pat. No. 4,049,545 "Chemical Waste Water Treatment Method" issued to Horvath Sep. 20, 1977, describes a chemical method of treating domestic, commercial, or industrial waste water that relies on the successive addition of a coagulant aid such as portland cement and precipitation aids such as aluminum sulfate and copper sulfate followed by potassium permanganate and ozone as oxidizing and disinfecting agents. Another example is U.S. Pat. No. 5,614,102 "Method for Purifying Water" issued to Sakurada Mar. 25, 1997, which relates to the use of at least two kinds of flocculants to treat sewage, followed by the use of at least three flocculants. Both processes are complicated enough to require continual monitoring of pH and other process parameters by a qualified operator.
Processes of varying scale have been explored. Municipal waste treatment plants, for example, utilize varying combinations of filtering, drying, chemical treating, digesting, and chemical treatment steps. These systems are enormous, and require large facilities permanently imbeded in the land. Conversely, processes on a much smaller scale have also been devised. U.S. Pat. No. 3,791,790 "Portable Purification Device for Fluids issued to Wyndham et al. Feb. 12, 1974 relates to a hand-held water purifier that uses a hand-operated diaphragm pump, filter, and a battery-operated germicidal lamp to eliminate microorganisms and particulates from small amounts of water. The scale of this device is not comparable to the present invention, as it is disclosed to produce 1.5 quarts of water per minute.
Closed loop systems have been attempted. U.S. Pat. No. 4,121,539 "Animal Enclosure System with Waste Treatment Means" issued Oct. 24, 1978 to Moore relates to a lagoon system that additionally uses airtight holding tanks for a waste stream, the first producing ammonia gas at ambient temperatures and the second for further digestion of the waste, where methane gas is produced.
The present inventor has developed a lagoon-less system, which is a precursor for the present invention, for recycling waste from animal houses which greatly improves the water quality of the effluent over that typically found in lagoon systems, variations of this system are disclosed below in FIGS. 2 and 3, and the discussion therewith. This is a closed loop system that utilizes aerobic bacteria. As such, the system still requires an air supply, bacteria, and extended residence time in a holding tank. Due the the presence of bacteria as an integral part of the system, licensed operators are required to monitor the system at least daily. Further, the closed loop system as disclosed in FIGS. 2 and 3 is much larger than the present invention, requires installation of permanent fixtures at the site, and would require further modification to produce potable water.
The present invention relates to an improved device and process for treating animal waste that is a closed loop system which yields water with greatly reduced carbon and nitrogen levels, and optionally, potable drinking water, plus solids that may be processed as fertilizer. The system does not require a lagoon or the addition of permanent structures to the land. It is relatively simple to monitor, and amenable to an electronic control system. It can produce a healthier environment for animals, and thereby increase profitability to the farmer.